Aims (1) Identify sources (geologic, point-source or regional-source pollution) of metals in soils, vegetation and groundwater of the Northeastern US using: (a) Pb isotopes (b) Elemental ratios of Cd, Ni, Cr, As, Cu and Zn (2) Establish metal mobility rates in terrestrial ecosystems utilizing greater than 100 years of atmospheric deposition records and evaluate potential release rates of metals into surface water, aquatic ecosystems and groundwater (a) Determine flushing times of Pb stored in the forest floor and other ecosystem compartments through the use of Pb isotopses (b) Determine flushing times of Pb, Cd, Cr, As, Ni, Cu and Zn using carbon-metal ratios and mass balance (3) Assess Pb, Cd, Cr, As, Ni, Cu and Zn concentrations in groundwater and surface water and identify the range of present human exposures possible for individual metals and for combinations of metals. (4) Combine the results of aims 1, 2 and 3 to develop scenarios for potential future human exposure to individual and combinations of metals in the Northeastern US.